Update uninstall.php to remove (unlink) all letsencrypt post, pre and renew hook script from /usr/local/bin. This is important so the future reinstallation of the scripts via ISPConfig will work. While at these I found two other ISPConfig scripts (ispconfig_patch and ispconfig_update_from_dev.sh) not removed but I won't add them here as I think they have a different function and I am not sure whether they should be removed (unlink).

- Improved installer and updater for multiserver mode. Modules and plugins were only configured if the selected service is available on the server.

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